The present invention relates to a particularly configured clutch tooth of a selector sleeve.
According to European publication EP 0 288 718 B1, all the clutch teeth of a selector sleeve of a gear wheel clutch for coupling a gear wheel to its shaft can be configured either in accordance with the generic type or symmetrically to the significant longitudinal center plane of the tooth in such a way that the respective reduced tooth flank portion is in the form of a recess in the side flank of the tooth. A corresponding undercut tooth flank portion of a clutch tooth of the gear wheel engages into this recess with radial overlap in the engaged state in order to prevent the selector sleeve from jumping back into its neutral position.
In known selector sleeve clutch teeth of the generic type in European publication EP 0 276 382 B1 and German Patent 845,903, the respectively reduced tooth flank portions are in the form of recesses in the side flanks of the tooth. In the case of the European publication, these recesses interact with undercut tooth flank portions and, in the case of the German patent, they interact with recesses in the side flanks of the clutch teeth of the gear wheel to prevent the selector sleeve from jumping out of the clutch toothing of the gear wheel. In these known clutch teeth with reduced tooth flank portions in the form of recesses in the side flanks of the tooth, the oblique end faces at the ends do admittedly merge into the respective recess by way of additional guide faces extending parallel to the significant longitudinal plane of the tooth, thus advantageously increasing the guiding length of the selector sleeve. In these known selector-sleeve clutch teeth, however, there is an unwanted increase in the engagement travel of the gear wheel clutch because the tooth portion extending axially between the recess and the end of the tooth requires an idle travel as spacing with respect to the gear wheel.
European publication EP 0 195 706 B1 discloses a selector sleeve of a gear wheel clutch for coupling a gear wheel to its shaft with non-generic clutch teeth without undercut tooth flank portions. In the clutch, the two mutually opposite flanks of each pair or the majority of pairs of successive clutch teeth alternately have two central thickened portions, between which one of the driver teeth associated in a manner fixed in terms of motion to the shaft engages in a displaceable manner, or two projections provided on the ends and extending out in the circumferential direction, the projections each entering into radial overlap, when the selector sleeve is moved into its coupled position, with an undercut tooth flank portion of a clutch tooth of the gear wheel in order to prevent the selector sleeve from jumping back into its neutral position. Apart from the fact that the projections of the clutch teeth of the selector sleeve have an unfavorable effect when passing through the locking toothing of the synchronizer ring, those clutch teeth in this known selector sleeve, which do not have central thickened portions but are only provided with the end projections, cannot exercise a guiding function, and the torque transmission capacity of the selector sleeve is thus impaired.
German publication DE 44 13 169 C1 discloses a clutch tooth of a selector sleeve of a gear wheel clutch for coupling a gear wheel to its shaft. The guide portion, which is arranged centrally in relation to the directions of the center line of the selector sleeve, is bounded in both peripheral directions of the center line by a respective guide face extending parallel to the center line. The guide portion can be introduced, so as to be axially displaceable and fixed in terms of rotation, into an axial driver toothing concentric with and fixed in terms of movement relative to the shaft. Each of the ends forming a boundary in the directions of the center line has two oblique end faces, which are arranged in a roof shape relative to one another, the common vertex edge of which lies in a significant longitudinal plane of the tooth containing the center line. The side flanks each comprise one guide face of the guide portion, a tooth flank portion which adjoins it in the direction of the center line towards one end and is at a reduced distance from the significant longitudinal plane of the tooth, and the oblique end face, which, like the guide face, lies on the same side of the significant longitudinal plane of the tooth and in which one oblique end face merges directly into an undercut tooth flank portion. In the direction of the guide portion, the undercut tooth flank converges with straight flank lines relative to the significant longitudinal plane of the tooth. The other oblique end face merges, in the direction of the center line towards the guide portion, into an overall guide surface which extends parallel to the center line and forms a continuous coherent surface with the guide-portion guide face on the same side of the significant longitudinal plane of the tooth and the distance of which from the significant longitudinal plane of the tooth is less than the distance of the guide-portion guide face on the other side of the significant longitudinal plane of the tooth from the significant longitudinal plane of the tooth.
The object on which the invention is based is essentially to avoid increasing the engagement travel (gear-change travel) as described while retaining an increased guiding length.
In the clutch tooth according to the invention, a third guide face is formed on one flank side in the region of one end. This guide face significantly extends the guiding length of the clutch tooth in the coupled position of the selector sleeve, with the result that the selector sleeve no longer sticks in the driver toothing associated with the shaft.
The clutch tooth according to the invention, in the initial state, is symmetrical with undercut tooth flank portions on both tooth flank sides on both sides of a longitudinal center plane of the tooth. The clutch tooth can be produced from a conventional clutch tooth by reducing the thickness of the tooth by a constant amount parallel to the center line of the selector sleeve, on one side of the originally central longitudinal plane of the tooth, to such an extent that a relatively short, separate, third guide face is formed on the end concerned.
An advantageous feature of the invention is that, the selector sleeve can be provided both with conventional clutch teeth with symmetrical undercut tooth flank portions and with clutch teeth according to the invention, with a third guide face in the region of the ends.
An additional advantageous feature of the invention is that the clutch teeth can be divided into two groups which initially, starting from a common initial tooth thickness, are all symmetrical and have the same dimensional shape and depth of the undercut tooth flank portions.
A first group of teeth comprises conventional symmetrical teeth which act in the customary manner as regards all the functions of toothing such as meshing, locking, releasing, idle travel and gear retention.
The thickness of the teeth of a second group is reduced on one side during the manufacturing process. The driver toothing associated with the shaft is thickened at the corresponding points by the amount removed from the selector sleeve, and the backlash thus remains unaltered. During the production of such a selector sleeve, the selector sleeve is initially symmetrical, i.e. has been broached with a group of initial teeth and rolled to give a uniform shape to the undercut tooth flank portions. In the subsequent operation, namely calibration broaching, both the small calibration amount and also, in addition, the tooth thickness are removed from the guide faces with a correspondingly designed broach to give the third guide face. This method is advantageous because, in contrast to conventional toothing, neither additional operations nor rolling of undercut tooth flank portions of different depths is required.
In gear wheel clutches for coupling a gear wheel to its shaft, it is customary to use an annular selector sleeve carrier which is arranged concentrically and fixed in terms of motion relative to the shaft, and which carries the driver toothing for the selector sleeve. Applying the invention to a gear wheel clutch of this kind, the selector sleeve and the driver toothing in this clutch can be configured in order to give symmetrical tooth gaps on the selector sleeve with in each case two asymmetrical clutch teeth lying symmetrically to the thickened driver tooth of the selector sleeve carrier. The advantage of a gear wheel clutch configured in this way lies in the simple configuration of the selector sleeve carrier obtained from external suppliers, which can thus be fitted as it arrives.
The invention is described in greater detail below with reference to an embodiment illustrated schematically in the drawing figures.